cppcheck : update rules

Cppcheck is currently failing in CI. This patch updates the rules to fix
some of the issues, the remaining ones will be fixed by a patch on the
tf-m repo.

Signed-off-by: Hugo L'Hostis <hugo.lhostis@arm.com>
Change-Id: I0c834b09bf0d9520524780eef2110e4f60f70e71
diff --git a/cppcheck/tfm-suppress-list.txt b/cppcheck/tfm-suppress-list.txt
index 809e636..0ab4fb6 100644
--- a/cppcheck/tfm-suppress-list.txt
+++ b/cppcheck/tfm-suppress-list.txt
@@ -1,5 +1,5 @@
 //-------------------------------------------------------------------------------
-// Copyright (c) 2018-2019, Arm Limited and Contributors. All rights reserved.
+// Copyright (c) 2018-2021, Arm Limited and Contributors. All rights reserved.
 //
 // SPDX-License-Identifier: BSD-3-Clause
 //
@@ -56,3 +56,11 @@
 *:*/lib/ext/*
 *:*/bl2/ext/*
 *:*/platform/ext/*
+
+//cppcheck shouldn't complain about unused function.
+unusedFunction
+
+//Variables in the following file are initialised to a specific value before being
+//modified. This is good practice and complies with TF-M guidelines. It should not
+//trigger an error.
+redundantInitialization:*/security_cnt.c